// 1.暴力解法,使用两个 for 循环
class Solution {
    public int[] twoSum(int[] nums, int target) {
        int n = nums.length;
        for (int i = 0; i < n; ++i) {
            for (int j = i + 1; j < n; ++j) {
                if (nums[i] + nums[j] == target) {
                    return new int[]{i, j};
                }
            }
        }
        return new int[0];
    }
}

// 2.使用Map
class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer,Integer> map = new HashMap<>();
        for(int i = 0; i < nums.length; i++){
            if(map.containsKey(target - nums[i])){
                return new int[]{map.get(target-nums[i]),i};
            }
            map.put(nums[i],i);
        }
        return new int[0];
    }
}